Ventricular Fibrillation (V-Fib)

What to do if someone collapses

V-fib can only be reversed by a shock, and the brain starts to die within minutes without blood flow. Bystanders make the biggest difference.

1. Check: tap and shout. If there is no response and no normal breathing, or only gasping, assume cardiac arrest.
2. Call 911 or your local emergency number and put the phone on speaker. Send someone to find an AED (automated external defibrillator), often found in airports, gyms, schools and offices.
3. Start chest compressions: heel of the hand in the center of the chest, push hard and fast, at least 2 inches (5 cm) deep, at 100 to 120 per minute, letting the chest recoil fully. Hands-only CPR is effective for adults.
4. Use the AED as soon as it arrives: turn it on and follow the voice prompts. It analyzes the rhythm and will only shock if it detects V-fib or a similar shockable rhythm. Make sure nobody touches the person during the shock.
5. Keep going until emergency services take over or the person starts moving and breathing normally.

Survival falls by roughly 7% to 10% for each minute without CPR and defibrillation. Immediate bystander CPR can double or triple the chance of survival.

What happens in the heart

Normally, an electrical signal starts in the heart's natural pacemaker and spreads in an orderly wave, making the ventricles contract together and pump blood. In V-fib, many disorganized electrical signals fire at once. The ventricles quiver at several hundred beats a minute but do not contract effectively. Blood pressure falls to zero.

V-fib often begins as ventricular tachycardia (a very fast but organized rhythm) that degenerates into chaos. Without a shock, it eventually becomes asystole (flatline), which is much harder to reverse.

V-fib vs A-fib

Symptoms and warning signs

V-fib itself causes sudden loss of consciousness with no pulse. In the minutes, hours or days before, some people have warning symptoms:

• chest pain or pressure, from a heart attack
• palpitations or a racing heartbeat
• dizziness or lightheadedness
• shortness of breath
• fainting, particularly during exertion

In many cases there is no warning, and V-fib is the first sign of heart disease.

Causes and risk factors

Most common

• Heart attack and coronary artery disease: lack of blood flow makes heart muscle electrically unstable. V-fib is the leading cause of death in the first hour of a heart attack.
• Scar tissue from a previous heart attack.
• Cardiomyopathy and heart failure, especially when the heart pumps weakly (ejection fraction 35% or less).

Inherited conditions (often in younger people)

• Hypertrophic cardiomyopathy
• Arrhythmogenic cardiomyopathy
• Long QT syndrome
• Brugada syndrome
• Catecholaminergic polymorphic ventricular tachycardia (CPVT)

Other triggers

• very low or high potassium, or low magnesium
• medicines that prolong the QT interval, and drug toxicity
• cocaine and methamphetamine
• electric shock and lightning
• drowning and severe lack of oxygen
• commotio cordis: a blow to the chest at a precise moment in the heartbeat, for example from a baseball
• myocarditis (heart inflammation)

Treatment

Emergency treatment

• Defibrillation: an electric shock that resets the heart's rhythm.
• High-quality CPR between shocks.
• Medicines given by paramedics or in hospital: epinephrine, and antiarrhythmics such as amiodarone or lidocaine.
• Airway support and oxygen.

After the heart restarts

• Coronary angiography and opening blocked arteries with stents if a heart attack caused it.
• Temperature control in intensive care to protect the brain.
• Correcting potassium, magnesium and other imbalances.
• Tests to find the cause: ECG, echocardiogram, cardiac MRI, blood tests and, in younger people, genetic testing.

Preventing a recurrence

• Implantable cardioverter-defibrillator (ICD): a small device placed under the skin, with wires to the heart, that detects V-fib and delivers a shock within seconds. It is recommended for most survivors of V-fib not caused by a reversible problem. Some people with high risk, such as severely weakened heart muscle, receive one before any event.
• Medicines: beta-blockers and, in some cases, antiarrhythmic drugs.
• Catheter ablation to destroy tissue that triggers dangerous rhythms.
• Treating the underlying disease, such as coronary artery disease or heart failure.

Outlook

Out of hospital, only about 1 in 10 people who have cardiac arrest survive to leave the hospital, but survival is much higher when V-fib is witnessed, CPR starts at once and an AED is used within a few minutes. Survivors who get an ICD and treatment of the cause can live long, active lives. Some survivors have memory or concentration problems, anxiety or depression, which rehabilitation can help.

Prevention

• Control blood pressure, cholesterol and diabetes, and do not smoke.
• Know the warning signs of a heart attack and call 911 right away.
• If you have heart failure or a past heart attack, ask whether an ICD is recommended.
• If a relative died suddenly and young, ask about screening for inherited heart conditions.
• Learn CPR and how to use an AED.

Frequently asked questions

Can you survive ventricular fibrillation?

Yes, if it is treated within minutes with CPR and a defibrillator shock. Survival is highest when someone witnesses the collapse, starts chest compressions immediately and an AED is used quickly. Without treatment, V-fib is fatal within minutes.

What is the most common cause of ventricular fibrillation?

The most common cause is coronary artery disease, especially a heart attack or scar tissue from a previous one. Other causes include cardiomyopathy, inherited rhythm disorders such as long QT and Brugada syndromes, severe electrolyte imbalances, certain drugs, electric shock and a blow to the chest.

What is the difference between V-fib and A-fib?

V-fib affects the lower chambers and stops the heart from pumping, causing cardiac arrest within seconds. A-fib affects the upper chambers. The heart keeps pumping, though irregularly. A-fib is common and raises stroke risk but is rarely immediately life-threatening.

What does an ICD do?

An implantable cardioverter-defibrillator continuously monitors the heart rhythm. If it detects ventricular fibrillation or dangerous ventricular tachycardia, it delivers a shock within seconds to restore a normal rhythm. It does not prevent the rhythm from starting, but it greatly reduces the risk of dying from it.

Can you do CPR wrong and make things worse?

For someone in cardiac arrest, doing CPR is far better than doing nothing. Broken ribs can happen and are expected, but they heal. Push hard and fast in the center of the chest, use an AED as soon as possible, and follow the dispatcher's instructions.